International Patent Publication No. WO 02/00105 (PCT/AU01/00775) disclosed a system for the testing of human eyesight that was substantially automated and which could be performed by the human subject using an appropriately programmed general purpose computer and without the need for or use of lenses interposed between the subject and a video display screen of the computer. The system operated by executing one or more application programs on the computer and, through interaction between the subject and sequences of graphical images displayed on the display screen by the executing programs, the computer would record the subject's responses. The recording of the responses guided the execution of selected programs to capture detailed test data equivalent to that which would traditionally be recorded by an optometrist performing a traditional eyesight examination with the aid of interposed lenses.
The testing regimen firstly involved a setup phase which essentially calibrated the optical system formed by the subject and the display screen. Specific tests performed included an acuity white E test, various astigmatism tests, near and distance acuity tests, a prefilter contrast test, a discrimination test, binocular tests, a saccades test as well as tests for cataracts, macular integrity, peripheral field and colour vision. The recorded data would be processed by the computer or remotely to calculate at least one aspect of the visual functioning of the subject to thereby enable determination of an optical corrective lens prescription suitable for the subject. The determination could be fully automated by computerised processing, assisted by a skilled optometrist, or performed in whole by the optometrist.
The system enabled subjects at home or in community clinics, for example, to directly access and benefit from vision testing without a need to visit an optometrist or involving the use of expensive lenses.
Astigmatism is a condition where a person's sight levels are in constant conflict for distance and near vision, with the eye reaching a point of equal blurring when neither distance nor close vision is perfectly clear. There is an irregularity to the optical surfaces of the eye that causes blurriness at all distances. The defect is similar to the distortion seen when looking through a cylindrical lens. Any lines seen through the lens that are near to parallel with the cylindrical lenses axis are seen as black, while any lines at an angle to the axis are blurred to a grey colour. This was shown in FIG. 10B of WO 02/00105, where the line 1010 indicated the axis of astigmatism.
Accuracy in any test procedure is always important. This is particularly so for astigmatism tests since astigmatism affects much of the population with less than perfect eyesight.